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  #16  
Old 20-11-12
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Re: Teleconverter conundrum

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I think it important we know the camera your relative is using, all cameras are not the same, auto focus sensitivity can vary between models and brands. Converters change the effective aperture, a f5.6 lens becomes a f8 lens with the 1x4 converter attached, very few cameras auto focus easily at this aperture. If David can try it before buying and it works satisfactorily that's fine.
We don't want David spending his hard earned cash rashly.

Patrick
I have just copied this from the Kenko web site word for word it reads:-

With the PRO 300 1.4x, DGX full AF operation is possible with camera lenses having a maximum aperture of F4 or brighter. The same light and contrast requirements apply.

This underlines the arguments I have been putting forward.

Patrick
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  #17  
Old 20-11-12
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Re: Teleconverter conundrum

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I have just copied this from the Kenko web site word for word it reads:-

With the PRO 300 1.4x, DGX full AF operation is possible with camera lenses having a maximum aperture of F4 or brighter. The same light and contrast requirements apply.

This underlines the arguments I have been putting forward.

Patrick
I have read this too, Patrick!

But regardless of what they say. I can absolutely assure you that the Kenko 300 Pro gives full auto focus in my experience!

We have tried, and used it on numerous occasions without fail.

It was used whether light conditions were good or not.

It works perfectly well on the Canon 70 - 300mm f4-5.6 USM

It works perfectly well on the Sigma 70 - 300mm f4 - f5.6

It works perfectly well on the Canon 55 - 250mm f5.6

The cameras used are the 7D 550D 400D
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  #18  
Old 20-11-12
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Re: Teleconverter conundrum

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2x converters of any quality do loose definition, how much will depend on how good the original optic. A converter is in simple terms a sophisticated magnifying class, so it magnify's deficiancies the original optic has, a 2x probably finds more than a 1x4. Not to mention the loss of two stops.
I have used a 2x and was not impressed.

Patrick
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Originally Posted by Garry View Post
I have read this too, Patrick!

But regardless of what they say. I can absolutely assure you that the Kenko 300 Pro gives full auto focus in my experience!

We have tried, and used it on numerous occasions without fail.

It was used whether light conditions were good or not.

It works perfectly well on the Canon 70 - 300mm f4-5.6 USM

It works perfectly well on the Sigma 70 - 300mm f4 - f5.6

It works perfectly well on the Canon 55 - 250mm f5.6

The cameras used are the 7D 550D 400D
This being then case then you are in a perfect position to advise David on how to tape the contacts to enable the converter to work, which was his original question.

Patrick
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  #19  
Old 20-11-12
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Re: Teleconverter conundrum

No tapes used!

Just attach it and use it!
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  #20  
Old 20-11-12
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Re: Teleconverter conundrum

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No tapes used!

Just attach it and use it!
I trust you will forgive be for pressing this further. Reasons for all this talk of taping the contacts is because the camera shuts off the AF when it detects a f5.6 or smaller aperture lens is attached, the taping is to prevent this happening.

Now as two of the lenses mentioned are f4-f5.6 this shut off would not necessarily happen as the camera sees f4, I can see the now effective f5.6-f8 working. I must however remain sceptical about the 250mm f5.6 the camera would see a f5.6 lens and should shut off the AF.

Patrick
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  #21  
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Re: Teleconverter conundrum

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I trust you will forgive be for pressing this further. Reasons for all this talk of taping the contacts is because the camera shuts off the AF when it detects a f5.6 or smaller aperture lens is attached, the taping is to prevent this happening.

Now as two of the lenses mentioned are f4-f5.6 this shut off would not necessarily happen as the camera sees f4, I can see the now effective f5.6-f8 working. I must however remain sceptical about the 250mm f5.6 the camera would see a f5.6 lens and should shut off the AF.

Patrick
It's not a problem, Patrick !

Needles to say that this teleconverter is attached in order to turn the lens into a longer lens.

The Canon or Sigma 70 - 300mm becomes a 420mm f8 lens. This teleconverter works perfectly well with this.

I agree that for those who are sceptical about this. The best option here would be to be able to borrow one and try it!

I am purely relaying, what I actually know to be a fact, as far as using a combination of these lenses, and the camera with this teleconverter.

I certainly would not advise anyone on something that is only hear say!

I also point out that the Kenko 300 pro, is the only teleconverter that I personally know of, that will do this.

I also have the Kenko x1.4 MC4. This teleconverter will NOT auto focus any lens slower than f4. That is to say that a lens of f4 - f5.6 will not auto focus with it.

Hope that helps.
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  #22  
Old 20-11-12
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Re: Teleconverter conundrum

Get an f/4 lens, then it will autofocus with any 1.4x teleconvertor.
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  #23  
Old 21-11-12
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Re: Teleconverter conundrum

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Get an f/4 lens, then it will autofocus with any 1.4x teleconvertor.
It's the answer of course, I have already suggested this but we have to consider the f4 version of the Canon 400mm is in the thousands of pounds. Not a price everyone can afford.

Patrick
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  #24  
Old 21-11-12
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Re: Teleconverter conundrum

I was thinking of proper f/4 lenses the 500mm or 600mm.
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  #25  
Old 21-11-12
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Re: Teleconverter conundrum

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I was thinking of proper f/4 lenses the 500mm or 600mm.
The Canon f4 500mm is over 8000 and the f4 600mm is over 10000 big money in anyone's book.
There is a cheaper option the Sigma f4.5 at 3700.

Patrick
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